Apparatus for producing refractory metals



Sept. 18, 1956 D. v. KELLER, JR, ETAL 2,

APPARATUS FOR PRODUCING REFRACTORY METALS Filed July 28, 1950 2 Sheets-Sheet i INVENTORJ' DOUGLAS v. KELLER JR. WILLIAM E. SHAW BY mm %TORN:EV2L

Sept. 1, 1956 D. v. KELLER, JR, ETAL 2,

APPARATUS FOR PRODUCING REFRACTORY METALS Filed July 28, 1950 2 Sheets-Sheet 2 INVENTORS DOUGLAS V. KELLER, JR. BY WILLIAM E, SHAW ATTOR EY' United States Patent Q APPARATUS FOR PRODUCING REFRACTORY METALS Douglas Vern Keller, In, Buffalo, and William Earl Shaw, 1 Niagara Falls, N. Y., assignors to National Lead Company, New York, N. Y., a corporation of New Jersey Application July 28, 1950, Serial N 0. 176,444 5 Claims. (Cl. 266-42) This invention relates to the production of refractory metals by reduction of compounds thereof. It is particularly concerned with apparatus useful for the reduction of halides of refractory metals such as zirconium and titanium by reaction with basic metals such as sodium, magnesium and the like.

It has heretofore been proposed to prepare titanium and zirconium in the form of sponge by reduction of the halides of these metals by an alkali or alkaline earth metal such, for example, as sodium, calcium or magnesium, the refractory metal sponge being obtained upon completion of the reaction in a solid mass mixed with the halide of the reducing metal and, in many cases, with some of the reducing metal itself. Extensive subsequent treatment which includes dissolving the reducing metal halides in water is required to free the reduced refractory metal product from the salt and it has been found difficult, if not impossible, to prevent some contamination of the metal product with oxide during such treatment. Since even very small amounts-of oxide in the metal produce excessive brittleness thereof and render the metal much less valuable, it is highly important that oxide contamination should be prevented as far as possible.

. The present invention has for its principal object the improvement of apparatus for the reductionof refractory metals such as zirconium and titanium from their halides with reducing basic metals such as sodium, magnesium, and the like without exposing the metal to air or water until it has been freedfrom substantially all of the other reaction products and excess reactants.

A further object of the invention is to provide means for draining the metal salt formed during the reduction of the titanium or zirconium halide in the processes mentioned above from the retort or reaction vessel intermittently during the course of the reaction or at the conclusion thereof.

Another object of the invention is to provide a process for producing a very pure refractory metal, such as zirconium or titanium by reduction of the halide of such metal at a high temperature, in which process the major portion of the impurities are separated in molten form from the refractory metal product at the conclusion of or during the reaction without exposing the product to air or moisture.

A still further object of the invention is to provide a process for intermittently draining from the reaction vessel the metal salt formed by reaction during the reduction with an alkali or alkaline earth metal of a titanium or zirconium halide to form the corresponding metal.

Other objects and advantages of the present invention will be perceived from the following description taken in conjunction with the accompanying drawings in which:

Figure 1 is a somewhat diagrammatic view, partly in section, of apparatus suitable for the production of refractory metals such as titanium and zirconium and embodying the invention of the present application;

controlling drainage from the retort shown and Figure 3 is a sectional view of a modified for controlling drainage from the retort.

v The apparatus for the production of refractory metals such as zirconium and titanium by the reduction of their respective halides, which is shown diagrammatically in Figure l, comprisesthree principal parts, a reactor or retort 11, .a condenser 13, and a receiver 15. The retort 11, within which the reduction reaction is carried out, preferably comprises a cylinder 17. At its top and bot tom, the cylinder 17 is provided with outwardly projecting annular flanges 21 and 23, respectively.

The condenser 13 is preferably cylindrical and approximately the same diameter as the reactor 11. Projecting outwardly at the upper and lower ends of the condenser are annular flanges 25 and 27, respectively. The flange 27 of the condenser 13 and the top flange 21 of the reactor 11 abut and are fastened together by suitable means such as the bolts 29.

Over the top of the cylindrical condenser 13 there is mounted a horizontal plate 31 which closes the upper, open end of the condenser .and is tightly held in place by means such as bolts 33 engaging the annular flange 25. The closure plate 31 is provided with a'plurality of spaced ports or openings 35,, 37, and 39, which provide for in Figure 1;

form of device communication between the inside and the outside of the condenser 13.

Adjacent the lower end of the reactor 11, as shown in Figure 1, there is provided a transverse, horizontal, interior diaphragm 41 which may be welded in place and is provided with an orifice or opening 42. This orifice is Figure 2 is a fragmentary section view of the means for preferably located at approximately the center of the diaphragm 41, but it may be located at any suitable or convenient, place therein. Removably mounted in the diaphragm 41 is a drain plate 43. An outwardly-extending annular flange 44 on the plate 43 fits and is received within an annular recess 45 around the opening 42 and thereby supports the plate 43 therein by its periphery. A plate 46, which is preferably removable for convenience in dismantling the retort, is spaced slightly above the diaphragm 41 and is supported by blocks 47 arranged around the periphery of the diaphragm. Perforations 48 are provided in the plate 46 over the drain plate 43. At its center the drain plate, 43 is provided with an orifice 49 which is surrounded by a downwardly projecting tubular spout 51 through which liquid in the reactor 11 can drain.

Drainage from the spout 51 is caught in the receiver 15 which preferably has a closed bottom 53 and a cylindrical wall 55. An outwardly-projecting, annular flange 57 is provided at the upper end of the receiver 15, this flange abutting and being clamped to the flange 23 of the reactor 11 by suitable means such as the bolts 59.

Passing through the wall 55 of the receiver 15 is a tube or pipe 61 which projects upwardly Within the receiver and which has a closed end 63 extending into the tubular spout 51 of the drain plate 43. The tube 61 is of smaller diameter than the spout 51 and does not, therefore close the spout but leaves a restricted annular passage 64 therein. Arranged within and spaced from the Wall of the pipe or tube 61 is a smaller tube 65 which has an open end 67 adjacent but spaced from the closed end 63 of the tube 61.

The reactor or retort 11 is provided with heating means on the outside thereof shown diagrammatically and indicated by the reference character 69. The manner of heating the retort is not critical. Depending upon the type of heating which may be most convenient in any specific installation, gas burners, oil burners or electrical heaters such as silicon carbide resistors may be employed. Around the condenser 13 there is provided a cooling jacket 'ilhaving connections 73 and 75 for the entrance and exit of a cooling fluid. L

In the production of titanium or zirconium with the *apparatus diagrammatically shown in Figure 1, after assembly of the reactor 11, receiver 15, and condenser shown). When desired, the. cooling fluid may be circulated through the dual tubes'65and 61, floWing inwardly through the former and passing into the tube 61 adjacent the closed end 63 thereof. The salt surrounding the closed end in the drain spout 51 may thus. be, cooled,

sufiiciently to keep it in'solid form even though the temperature of the reactor 11 is above the melting point 0f the salt.

The cover plate31 is then secured in place on top of I the condenser 13 and. the apparatus is evacuated by a vacuum pump (not shown) attached to a line .77 which is secured in the opening 35 provided in the oover31.

An auxiliary line 79, controlled by a stop-valve 80, which is connected externally of the vessels to the receiver 15 through an opening 81 in the wall 55 thereof, branches l frornthe line 77 fand thus, provides means for the evacuae I tion'of the receiver 15 and the portion of the reactorll below the diaphragm '41." While the apparatus is being I evacuated, the temperature of the reactor is raised by the heating device 69 to assist in driving out gases and moisture in the apparatus. I I I The pressure within the apparatus is then reduced by the vacuum pump sufiiciently to insure the presence the tubular drain spout 51 around the tube 61 andover its closed end 63. Since the salt plug is maintained: in

4 i During the reaction additional reducing metal may be introduced from time to time through the inlet 83' and the refractory metal tetrachloride may be fed intermit- 'tentlyor continuously through the line 85 The reactions involved are exothermic ones and hence, while it is necessary to heat the reacting materials to initiate the reaction, once the reaction has started it is possible under favorable conditions to reduce or suspendthe supply of external heat, The reaction rate, is preferably so regulated by varying the rate of flow of thetetrachloride or other halide thattheheat evolved by the reductionmaintains the temperature in the'reactor 11 between about 16009-1 and1550 ,F. although higher temperatures, within the limitations of the apparatus,may be employed. I

When for any reason the process is to be interrupted, it is desirable that the magnesium or other reducing metal in the reactor should be substantially used up. Consequently, no further reducing metal is added although j the'feed of tetrachloride into the reactor is continued,

until increasing pressure; in the system indicates that no further reaction is occurring. At this point, the addition of the tetrachloride is discontinued and the reducing metal chloride in the retort 11 is allowed to drain into the receiver 15.

Draining of the reducing metal salt is permitted by melting out the plug of salt'iirozen in the orifice 49 and the solid state only by the cooling fluid circulating in; the tubes 65, and 61, it ,is-onlyneces'sary to stop such circulation to'cause the plug to be quickly melted by the heat of the reactor. Thereupon, most'of' the molten salt and reducing metahif any, contained, in the reactor 11 will drain into the receiver 15 through the annular passage therein of no more'than the slightest traces of moisture j or air. When the tightness of all connections has been established by leak-rate tests an inert gas such as argon I or helium is admitted to the vessels through the lines 77 and 79. The pressure of inert gas maintained in the apparatus during the reaction may vary within a range on either side of atmospheric pressure. In general absolute pressures between about 650 and 900 mm. of mercury are suitable. It will be recognized that the operating temperature of the retort 11 will be one of the factors considered in controlling the internal pressure of inert gas since the pressure should be great enough to minimize volatilization of the reducing metal. It will also be recognized that the use of inert gas at a positive pressure, i. e. above 760 mm. of mercury, will prevent any possible leakage of air into the apparatus. 7

A suitable amount of the reducing metal which is to be used, such as sodium or magnesium, is then introduced through the inlet 83 connected to the opening 37 of the cover plate 31. In admitting the reducing metal, which may be in either solid or liquid form, care should be taken to avoid introduction of moisture or air into the apparatus.

The apparatus is now ready for the starting of the reduction reaction and the temperature of the reactor 11 is raised by heat supplied from the heating means 69. When the desired temperature is reached in the retort, which may be as low as 1450 F. although somewhat higher temperatures-from about 1500 F. to 1650 F.- are preferred, the refractory metal halide, preferably the tetrachloride, which is to be reduced is introduced into the reactor 11 through the line 85 which is connected to the opening 39 in the cover plate 31. The reactor is, of course, far above the temperature at which the tetrachloride is changed to vapor and it therefore reacts easily with the molten reducing metal to form the chloride thereof and to leave the refractory met-a1 in theform of a sponge. If desired, the refractory metal halide may be vaporized and then admitted to the reactor 11 as a gas.

64. The speed of draining may be increased in; some cases :by creating a pressure differential between the re- I actor 11 and condenser 13 and thereceiver 15; This may beaccomplished either by increasing the pressure of inert. gas above the diaphragm 41 or by reducing the pressure below it.

The apparatus is then evacuated again, this time to an absolute pressure of less than 100 microns of mercury and the temperature of the reactor is raised to about l850 F.2000 F. and held in that range for a substantial period of time, preferably at least an hour and a half. Virtually all the salt and reducing metal which may remain in the refractory met-a1 sponge are thus vaporized and collected in the cooled condenser 13, leaving in the reactor on the perforated plate 46 a highly purified titanium or zirconium as the case may be. The pressure maintained in the apparatus during the distillation of the impurities should be as low as practicable since the efficiency of the purification will thereby be increased.

When the distillation of the impurities is completed, the heating of the reactor 11 is discontinued and the apparatus is permitted to cool to room temperature. To

prevent the possibility of oxidation of the product it is preferred to establish in the system a positive inert gas pressure during the cooling period. If desired, however, the vacuum in the system during the distillation may be maintained while the apparatus and product cool. The apparatus is then disassembled and the refractory metal sponrm may be removed from the reactor.

The following specific examples illustrate the operation of the above described process:

Example 1 This was a titanium recovery of approximately 90%. The product was ductile and of a high degree of purity, analysis showing less than 0.4% of impurities.

Example 2 In apparatus embodying the present invention pounds of zirconium tetrachloride were reduced by magnesium. The reactor was then drained of most of the magnesium chloride and subsequently the remaining magnesium chloride and the traces of magnesium remaining in the reactor were distilled off during a period of about two hours at a temperature of approximately 1990 F. under vacuum, a pressure of 5 microns of mercury being maintained. Zirconium sponge weighing 4.25 pounds was recovered. This represented a yield of 73%. The zirconium product obtained was very pure and ductile.

It will be evident that with the apparatus described above the reduction process may be so operated that the metal salt formed by reduction of the refractory metal halide may be intermittently drained from the reactor 11 into the receiver 15. This is readily accomplished by reestablishing circulation of the cooling fluid through the tubes 61 and 65 after some of the molten salt has drained from the reactor and thus causing solidification of salt in the orifice 49 and the spout 51 around the end 63 of the tube 61. Intermittent draining has the advantage of permitting utilization of the equipment to its full capacity by preventing the accumulation of large amounts of the molten reducing metal salt in the reactor while at the same time preventing any possibility of substantial quantities of the reducing metal being lost through the drain spout 51. Another advantage which results from preventing the collection in the retort 11 of alarge quantity of reducing metal salt is that the refractory metal sponge produced is more dense.

In Figure 3 there is shown a modified form of drain which may be employed instead of the arrangement shown in Figures 1 and 2. The modification comprises a drain plate 91, corresponding to the plate 49, having a peripheral, outwardly projecting flange 93 set in a recess 95 in the diaphragm 41. The plate 91 is provided with a centrally located bore 97, the walls of the upper portion of the bore being offset and tapered as shown at 99. The bore or orifice 97 is closed by a bead or button 101 of a metal which must fuse at a temperature below that of the drain plate 91. Nevertheless, metal used to form the button 101 should have a melting point above the normal operating temperature of the reactor 11 but sufficiently low so that, without damage to the reactor or disturbance of the process, the temperature of the reactor may be raised high enough to cause the button 101 to fuse and open the orifice or bore 97 and thus permit the salt accumulated in the reactor to drain through the orifice into the receiver 15.

Silver, which has a melting point of 1761" F. is one metal which has been found suitable for forming the plug or button 101. A number of alloys are also suitable for this purpose. Among such alloys are the following:

Melting point in F.

Mg 42%, Si 58% 1740 Ni 62%, Si 38% 1770 Fe 45%, Sb 55% 1825 Ni 40%, Mn 60% 1840 essentially the same as that heretofore describedv connection with the fusible salt plug. However, no cooling of the metal plug 101 is required during the course of the reaction and it is melted out to permit drainage of the reducing metal salt by increasing the temperature of the reactor 11 rather than by discontinuing the flow of a cooling fluid. It is evident that when a fusible metal plug of the type just described is used intermittent drainage of the reducing metal salt from the reaction chamber or retort in the manner described above cannot be used. It should be noted, however, that in the form of apparatus shown in Figures 1 and 2 magnesium or other reducing metal from the retort 11 may be solidified by cooling around the tube 61 in the drain plate 44 and that the metal plug thus formed will function in the samemanner as a solidified salt plug.

Preferably the parts of the retort 0r reactor 11 in contact with the metals and fused salt are formed of stain: less steel while the condenser 13 and receiver 15 which are not directly subjected to high temperatures may be constructed of ordinary steel. The flanged connections between the reactor 11 and the condenser and receiver may be provided with gaskets (not shown) of conventional type to insure their tightness and, if necessary, the flanges may be provided with cooling means (not shown) for preventing damage to the gaskets.

As will be apparent from the foregoing, the present invention provides novel means for the production of refractory metals such as zirconium and titanium in an extremely pure form. There are also provided a number of advantages in operation over the prior reduction processes for obtaining such metals. The apparatus employed is simple and comparatively inexpensive and the process in which the apparatus is used is easily carried out.

It should be recognized that the apparatus illustrated in the drawings is diagrammatic and that it is not intended to show all of the well known details of construction which would be required in the building of apparatus for carrying out the present invention. The invention has been described above with respect to the production of refractory metals such as zirconium and titanium in pure form. Nevertheless, it will be understood that substantially identical apparatus may be employed in producing pure alloys of titanium and zirconium as well as in the production of other metals, such as hafnium, tantalum, columbium, and vanadium, whose halides are reducible by alkali or alkaline earth metals and whose melting points are above that of the reducing metal halide formed. Obviously, such metals may also be produced as alloys with each other or with titanium or zirconium.

Various changes may, of course, be made in the construction of the apparatus and the operation thereof Without departing from the spirit of the present invention. Consequently, it is desired that the invention should not be considered limited except by the terms of the appended claims.

We claim:

1. In apparatus for the production of refractory metals, a retort, said retort providing a reaction chamber and having a bottom, a cover closing the upper end of said retort, a receiver directly beneath this retort and detachably sealed thereto, means connected to said retort to admit reactive materials to said chamber, heating means for supplying heat to said retort, cooling means for cooling a portion of said cover, means for draining a liquid reaction product from said retort into said receiver, said drain means providing the only direct communication between said retort and said receiver and comprising a drain opening in said retort bottom and a removable plug a and independent of said drain means for retaining a solid reaction product therein.

2. Apparatus as set forth in claim 1 in which said drain means comprises a removable member in the bottom of said retort having a drain opening therein.

3. Apparatus as set forth in claim 1 in which there is provided means directly connected to said receiver for removing air therefrom and admitting an inert gas thereto.

4. In apparatus for the production of refractory metals, a retort, said retort providing a reaction chamber and having a bottom secured thereto, a cover closing the upper end of said retort, a receiver directly beneath said retort and detachably sealed thereto, means connected to said retort to admit reactive materials to said chamber, heating means for supplying heat to said retort, coolingmeans for cooling 9. portion of said cover, means directly connected to said retort to remove air therefrom and admit an inert gas thereto, means directly connected to said receiver to remove air therefrom and admit an inert gas thereto, a perforated plate within said retort and spaced above said bottom to retain a solid reaction product within said retort, and means for draining a liquid reaction product from said retort into said receiver, said drain means providing the only direct communication between said retort and said receiver and comprising a drain opening in said retort bottom and a removable, easily fused plug in said opening, said plug when in place serving to interrupt all direct communication between said retort and said receiver and being removable by thermal action to permit such communication.

5. Apparatus as set forth in claim 4 in which said drain means comprises a removable member in the bottom of said retort having a drain opening therein.

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